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From: "adhemerval.zanella at linaro dot org"
 <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug time/30200] time sometimes appears to go backwards
Date: Tue, 21 Mar 2023 16:02:36 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D30200

--- Comment #14 from Adhemerval Zanella <adhemerval.zanella at linaro dot o=
rg> ---
(In reply to Bruno Haible from comment #13)
> (In reply to Adhemerval Zanella from comment #12)
> > So this problem *always* existed
>=20
> From "This problem always existed" you cannot imply "This problem never
> caused trouble, otherwise it would have been reported".

I will quote myself "I completely agree with you [Paul] that this is
problematic"
to make it clear I agree this is a problem.  I even sent a fix to make it u=
se
the same clock for all time interface that does not specify the clock id [1=
],
although I ended up retiring it because Florian explicit say he would rever=
t it
on RH distros because of performance implications.=20

[1] https://sourceware.org/pipermail/libc-alpha/2023-March/146088.html

>=20
> In https://sourceware.org/pipermail/libc-alpha/2023-March/146219.html I
> explain:
>=20
> On a typical system, there are
>   - hundreds of programs that call gettimeofday() or timespec_get(),
>   - hundreds of programs that call time().
> Each time a program calls gettimeofday() or timespec_get(), and then,
> within 1 to 3 milliseconds, a program (the same or a different one)
> calls time(), there is the potential for trouble because the time
> appears to go backwards. This trouble can occur with probability
> between 0.1% and 0.3%.
>=20
> This is the kind of trouble that does occur, but that people don't report
> because
> - it occurs only 1 in 300 to 1000 times,
> - it is nearly impossible to track down to glibc, since it will appear as=
 an
> interoperation bug between two different programs in the first place.

--=20
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